Is my thinking really that backward? In today's military, what is the ratio of supporting to combat roles? I think it's pretty significant, and good deal higher than one to one. In a situation where there was a general draft, there would be plenty of danger to go around, and not just for combat volunteers.
I agree that many military volunteers do consider combat to be a job they want, but I'd submit that in a mobilization, many draftees would prefer not to get that job.
The logic used to determine the prior lawsuit, as I understand it, was opposite to your line of thought. Perhaps the thought has to be modified, but if a draft is required, then the support to combat ratio changes from the volunteer force.